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i• ` <br /> l� ernoranduM 40e <br /> s� <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION <br /> 3443 Routier Road Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS: 8-495-5600 <br /> TO: Antonia K. J. Vorster FROM: Gary A. Reents <br /> Senior Engineer Project Engineer <br /> DATE: 17 June 1987 SIGNATURE: <br /> SUBJECT: SOIL AND GROUND WATER ASSESSMENT REPORT, TEIC#IERT CORPORATION, <br /> STOCKTON, SAN JOAQUIN COUNTY <br /> I have reviewed the subject report, dated 27 April 1987, prepared by Kleinfelder <br /> and Associates. My comments are as follows: <br /> 1. The soil contamination contours delineated on Plates 27 through 49 are not <br /> realistic. The vertical profiles show the zero contour at or near the <br /> water table which is contradictory to the data. The horizontal contour <br /> maps are more the result of analyzing different samples at different depths <br /> than of actual contamination differences. <br /> Looking at the raw data, it appears that the horizontal and vertical <br /> extent of contamination has been adequately defined. The interpretation of <br /> this data was simply overextended. <br /> 2. The statement that excavation of contaminated soil below 16 feet is not <br /> cost-effective is not supported. Although I agree that approximately 75% <br /> of the total mass of contamination is in the upper 16 feet, the concentra- <br /> tions and total mass of concentrations in the soils below 16 feet is still <br /> significant. The entire source (contaminated soils) of ground water <br /> pollution must be mitigated, especially since ground water levels are <br /> already significantly above State Action Levels. <br /> 3. Samples from all three monitoring wells installed contain levels of <br /> contaminants exceeding State Action Levels. As a result, the ground water <br /> work should change from a determination phase to a delineation phase. This <br /> should include, as a minimum: <br /> a. Identification and sampling of private wells surrounding the site <br /> (both up- and downgradient) for public health protection. <br /> b. Collection of information for private wells identified in Comment 3.a <br /> above ( total depths, screened intervals, pumping capacity, pumping <br /> schedule, etc. ) and assessment of the information to determine the <br /> potential affect of nearby wells on on--site ground water flow <br /> directions. <br />